1. Field of the Invention
The present invention relates to a build off self-test (BOST) testing method. More particularly, the invention relates to a method for performing tests at high speeds with high precision, and to a socket and a semiconductor device for use with that method.
2. Description of the Background Art
One way to facilitate device testing procedures has been known conventionally as BOST (Build Off Self Test). The BOST involves mounting on a test board an LSI or circuits for expediting examinations of a device under test (called the DUT hereunder, including an LSI or the like to be tested in bare-chip or packaged form). As such, the BOST is designed to carry out tests on high-performance multi-function DUTs by use of an unsophisticated low-performance tester.
In a typical testing setup, a high-frequency oscillator is mounted on the test board so that a clock signal generated thereby is used to perform tests on a DUT at frequencies higher than the tester frequency. In another setup, an operation amplifier is mounted on the test board so as to test analog signals.
FIG. 14 is a schematic view of a setup in which to practice a conventional BOST method. Referring to FIG. 14, an LSI 1008 for use with the BOST (LSI or the like under test in bare-chip or packaged form, called the BOST LSI hereunder) receives a simple control signal from a tester 1001. In turn, the BOST LSI 1008 generates test signals necessary for testing a DUT 1007, checks to see if output signals from the DUT 1007 are correct, and notifies the tester 1001 of the results of the tests on the DUT 1007.
The BOST LSI 1008 and DUT 1007 are mounted on different sockets 1012 attached to a test board 1003 and exchange relevant signals through printed wiring 1010. The BOST LSI 1008 and DUT 1007 use paths indicated by broken lines in the printed wiring 1010 in order to receive from the tester 1001 the power necessary for their operations. The tester 1001 thus causes the BOST LSI 1008 to operate.
Furthermore, the DUT 1007 uses the printed wiring 1010 indicated by solid lines to exchanges signals with the BOST LSI 1008 for testing.
Part of the signals input and output to and from the DUT 1007 may be exchanged directly with the tester 1001. This arrangement is intended to alleviate loads on the BOST LSI 1008.
In the conventional BOST setup outlined above, the BOST LSI 1008 and DUT 1007 are mounted on different sockets 1012 and exchange signals therebetween via the printed wiring 1010. This has led to problems such as a mismatch of impedance due to contactors 1006 of the different sockets 1012, or signal delays over the printed wiring 1010.
The present invention has been conceived to solve the previously mentioned problems, and general a object of the present invention are to provide a novel and useful testing method, a socket for use with the method, and a semiconductor device for use with the method.
The above object of the present invention is achieved by a testing method for use with a BOST setup. In the method, there are mounted on a single socket a BOST semiconductor device and a semiconductor device under test. The semiconductor device under test is tested using the BOST semiconductor device.
The above object of the present invention is also achieved by a socket for use in a BOST setup. The socket includes a socket body with a space to accommodate a first semiconductor device. A first cap with a space to accommodate a second semiconductor device is provided so as to push electrodes of the first semiconductor against contactors. A second cap pushing electrodes of the second semiconductor device against the electrodes of the first semiconductor device is also provided.
The above object of the present invention is further achieved by a semiconductor device for use in a BOST setup described below. The semiconductor device includes a BGA structure having conductive elastic elements attached to electrodes instead of solder balls.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.